Process for repairing asphalt pavement

ABSTRACT

This invention provides a process for repairing and surfacing broken asphalt pavements which involves applying to the distressed pavement a binder composition which has exceptional solvating power for asphaltic material, and which functions to solubilize and incorporate aged pavement asphalt into the binder composition as it penetrates and fills void spaces. 
     Illustrative of a preferred binder composition which is applied to the distressed pavement is a homogeneous blend of (1) a FCC main column bottoms residuum boiling above about 650° F., and (2) an asphalt-soluble elastomer which improves the elasticity and wear resistance of the binder composition.

This is a division, of application Ser. No. 45,480 filed June 4, 1979now U.S. Pat. No. 4,278,469.

BACKGROUND OF THE INVENTION

Asphalt road pavements are being subjected to increasingly severe loadstress. The repeated deflection of the road pavement causes elastic-typefailure and fatigue failure in the pavement, which manifests itself inthe form of pavement surface cracking and fracturing patterns.Conventional repair methods involve asphalt overlays, or replacement ofthe pavement surface.

A variety of paving grade asphalt compositions have been developed forthe purpose of providing improved physical and mechanical properties inpavements under heavy traffic loads. Illustrative of these developmentsare the asphalt compositions disclosed in U.S. Pat. Nos. 2,871,212;3,338,849; 3,374,104; 3,821,144; 3,879,323; 4,105,612; and the like.

Also of increasing importance for reasons of economy and convenience aremethods and materials for repairing and surfacing broken asphaltpavements. An important objective has been the development of materialsfor repair of asphalt pavements which exhibit increased flexibility andresistance to fatigue failure. Efforts to provide asphaltic bindermaterials with the desired elastomeric properties for asphalt pavementrepair are typified by the technology of U.S. Pat. Nos. 2,310,972;3,578,001; 2,700,655; 3,049,836; 3,253,521; 3,270,631; and 3,340,780.

U.S. Pat. No. 3,891,585 discloses an elastomeric pavement repairmaterial which consists essentially of a jellied blend of a paving gradeasphalt and a non-oil resistant asphalt-soluble rubber.

U.S. Pat. No. 3,919,148 discloses an elastomeric pavement repairmaterial which is the reaction product of paving grade asphalt,asphalt-soluble rubber, and a low viscosity asphalt solvent.

U.S. Pat. No. 4,021,393 describes an elastomeric pavement repairmaterial which is the reaction product of paving grade asphalt, non-oilresistant rubber, and petroleum maltenes.

There remains a need for an asphaltic cement material adapted for repairof asphalt pavements which is economical and conveniently workable underroad repair conditions, and which exhibits an improved combination ofelasticity and wear resistance properties.

Accordingly, it is a main object of this invention to provide animproved asphaltic binder composition adapted for the repairing andsurfacing of distressed asphalt pavement surfaces.

It is another object of this invention to provide a novel asphalticcomposition which is composed of low value petroleum refinery residuumand scrap polymeric material.

It is a further object of this invention to provide a process forrepairing and surfacing broken pavements, in which process the agedasphalt of the pavement surface becomes dissolved and incorporated intoa liquid binder composition which is applied to the pavement surface asa repair vehicle.

Other objects and advantages of the present invention shall becomeapparent from the accompanying description and disclosure.

DESCRIPTION OF THE INVENTION

One or more objects of the present invention are accomplished by theprovision of a process for repairing and surfacing broken asphaltpavements which comprises applying a fluid asphaltic binder compositionto a distressed pavement surface in a sufficient quantity to penetrateand fill void spaces, wherein said asphaltic binder compositioncomprises a homogeneous blend of (1) a highly aromatic solvent componenthaving a boiling range above about 650° F. and having a hydrogen contentdistribution in which the H_(Ar) proton content is between about 30 and50 percent, the H.sub.α proton content is at least 30 percent and theH.sub.α /H.sub.β proton ratio is above about 1.4; and (2) between about1-20 weight percent of a polymeric component which is substantiallysolvated by the solvent component and which imparts improved elasticityand wear resistance to the binder composition.

The asphaltic binder composition which is employed in the process isapplied to the surface of distressed asphalt pavement in a sufficientlyliquid form to penetrate and fill the interstices of the brokenpavement. Usually this is facilitated by heating the binder compositionto a temperature close to or above its softening point.

After the binder composition has been applied and has cooled to a firmset, the resultant repaired pavement exhibits excellent resistance tofatigue failure. The binder composition retains good elasticity,cohesion and adhesiveness properties under heavy stress conditions, evenwhen applied to orthotropic surfaces such as bridge pavements.

As described more fully hereinafter, a unique aspect of the presentinvention process and asphaltic binder composition is the exceptionalsolvating power of the highly aromatic hydrocarbon solvent compound ofthe binder composition for asphalt and polymeric materials. When thebinder composition is applied to a pavement surface in liquid form, thehighly aromatic hydrocarbon solvent extracts the aged paving gradeasphalt of the roadway into solution. The resultant plastic asphalticmedium sets into a relatively unitary structural mass. The cracks andvoids in the pavement are effectively "healed" rather than simplyfilled.

Highly Aromatic Hydrocarbon Solvent Component

The hydrocarbon solvents preferred for the preparation of the presentinvention asphaltic binder composition are thermally stable, highlypolycyclic aromatic mixtures having a boiling range above 650° F. whichresult from one or more petroleum refining operations. Representativehighly aromatic hydrocarbon solvents include FCC main column bottoms;TCC syntower bottoms; alkane-deasphalted tar; coker gas oil; heavy cycleoil; FCC main column clarified slurry oil; mixtures thereof, and thelike.

A highly aromatic hydrocarbon solvent such as a fluidized catalyticcracking (FCC) "main column" bottoms or a thermofor catalytic cracking(TCC) "syntower" bottoms contains a substantial proportion of polycyclicaromatic hydrocarbon constituents such as naphthalene,dimethylnaphthalene, anthracene, phenanthrene, fluorene, chrysene,pyrene, perylene, diphenyl, benzothiophene, and the like. Suchrefractory petroleum media are resistant to conversion to lowermolecular products by conventional non-hydrogenative procedures.Typically, these petroleum refinery residua and recycle fractions arehydrocarbonaceous mixtures having an average carbon to hydrogen ratioabove about 1:1, and a boiling point above about 450° F. For thepurposes of the present invention, the hydrocarbon constituents of apetroleum refinery residua or recycle fraction or the like which boilbelow about 650° F. are removed by distillation to provide a highlyaromatic hydrocarbon mixture which contributes the desired combinationof viscosity properties and solvation power to the invention asphalticbinder composition.

"FCC main column bottoms" and "TCC syntower bottoms" are obtained aspetroleum refinery residual streams from gas oil catalytic crackingoperations.

In a FCC operation, preheated gas oil is charged to a reactor inletline, where it picks up finely divided (e.g., 100 mesh) regeneratedcatalyst from the regenerator-catalyst standpipe and carries it into thereactor. Sensible heat of the gas oil charge plus sensible heat of hotcatalyst from regeneration at temperatures upwards of 1200° F. supplysufficient heat to sustain the endothermic cracking reaction at adesired temperature. The upward flow of hydrocarbons in the FCC reactoris adjusted to maintain a fluidized bed of the finely divided catalyst,thereby promoting contact between catalyst and charge. In a typicaloperation, California heavy gas oil (650° F.-1000° F.) is converted overa zeolite catalyst (e.g., as described in U.S. Pat. No. 3,140,249) in anFCC operation at 950°-975° F., a weight hourly space velocity of 11 anda catalyst to oil ratio of 8. Reaction products are then passed into adistillation column, in the bottoms section of which they are quenchedto about 600° F. to condense the heaviest hydrocarbons. Quenching isaccomplished by circulating heavy condensate through a cooler and thenback through the bottoms section of the column. The circulatingcondensate scrubs catalyst fines out of the up-flowing reactionproducts. The catalyst slurry so produced is sent to a settler toconcentrate the catalyst, and the concentrated catalyst is separated andreturned to the reactor. The oil separated from the concentrated bottomsis referred to as "FCC main column bottoms" or "FCC bottoms" or"clarified slurry oil", and is suitable for further processing inaccordance with the practice of the present invention.

In a TCC operation, catalyst pellets of one-sixteenth inch diameter movedownwardly through a reactor as a compact bed. In most modern TCC units,flow of gas oil charge is concurrent with catalyst flow in the reactor.As in FCC, heat of endothermic reaction is supplied by sensible heat ofgas oil charge and catalyst. After charging wide cut gas oil (400°-1000°F.) from mixed Canadian crudes and employing a catalyst (e.g., asdescribed in U.S. Pat. No. 3,140,249) at 875°-925° F. and a liquidhourly space velocity of 2 and a catalyst-to-oil ratio of 5, the reactoreffluent is fractionated to provide a TCC bottoms fraction (i.e.,"syntower bottoms") having a boiling range above 650° F., which issuitable for use as the highly aromatic hydrocarbon solvent component ofthe present invention asphaltic binder composition.

The nominal properties of various highly aromatic refining petroleumstreams prior to the removal of hydrocarbon substituents boiling belowabout 650° F. are as follows:

    ______________________________________                                        Syntower Bottoms                                                              ______________________________________                                        Sulfur                 1.13%                                                  Nitrogen               450 ppm                                                Pour Point             50° F.                                          5% Boiling Point       640° F.                                         95% Point              905° F.                                         Conradson Carbon       9.96                                                   ______________________________________                                    

    ______________________________________                                        FCC Clarified Slurry Oil                                                      ______________________________________                                        Sulfur                 1.04%                                                  Nitrogen               440 ppm                                                Pour Point             50° F.                                          5% Boiling Point       630° F.                                         95% Point              924° F.                                         Conradson Carbon       10.15                                                  ______________________________________                                    

    ______________________________________                                        Heavy Cycle Oil                                                               ______________________________________                                        Sulfur                 1.12%                                                  Nitrogen               420 ppm                                                Initial Boiling Point  373° F.                                         95% Point              752° F.                                         Conradson Carbon       10.15                                                  ______________________________________                                    

A typical FCC main column bottoms stream (or FCC clarified slurry oil)contains a mixture of chemical constituents as represented in thefollowing mass spectrometric analysis:

    ______________________________________                                                                    Naphthenic/                                       Compounds         Aromatics Aromatics                                         ______________________________________                                        Alkyl Benzenes    0.4                                                         Naphthene Benzenes          1.0                                               Dinaphthene Benzenes        3.7                                               Naphthalenes      0.1                                                         Acenaphthenes,(biphenyls)   7.4                                               Fluorenes                   10.1                                              Phenanthrenes     13.1                                                        Naphthene phenanthrenes     11.0                                              Pyrenes,fluoranthenes                                                                           20.5                                                        Chrysenes         10.4                                                        Benzofluoranthenes                                                                              6.9                                                         Perylenes         5.2                                                         Benzothiophenes   2.4                                                         Dibenzothiophenes 5.4                                                         Naphthobenzothiopenes       2.4                                               Total             64.4      35.6                                              ______________________________________                                    

Prior to removal of the light ends boiling below about 650° F., atypical FCC main column bottoms stream has the following nominalanalysis and properties:

    ______________________________________                                        Elemental analysis, Wt. %:                                                             C   89.93                                                                     H   7.35                                                                      O   0.99                                                                      N   0.44                                                                      S   1.09                                                                      Total                                                                             99.80                                                            ______________________________________                                               Pour Point, °F.:                                                                  50                                                                 CCR, %:   9.96                                                         Distillation:                                                                        IBP, °F.:                                                                         490                                                                5%, °F.:                                                                         640                                                                 95%, °F.:                                                                        905                                                          ______________________________________                                    

FCC main column bottoms are obtained (as noted above) by the catalyticcracking of gas oil in the presence of a solid porous catalyst. A morecomplete description of the production of this petroleum fraction isdisclosed in U.S. Pat. No. 3,725,240.

The ability of a highly aromatic hydrocarbon solvent to solvateasphaltic and polymeric materials can be expressed in terms of specifictypes of hydrogen content as determined by proton nuclear magneticresonance spectral analysis. Nuclear magnetic resonance characterizationof heavy hydrocarbon oils is well developed. The spectra (60 μc/sec) aredivided into four bonds (H.sub.α, H.sub.β, H.sub.γ and H_(Ar)) accordingto the following frequencies in Hertz (Hz) and chemical shift (δ):

    ______________________________________                                               H.sub.α                                                                        H.sub.β                                                                           H.sub.γ                                                                            H.sub.Ar                                    ______________________________________                                        Hz       0-60     60-100   120-200  260-560                                   δ  0-1.0    1.0-1.8  2.0-3.3  6.0-9.2                                   ______________________________________                                    

The H_(Ar) protons are attached to aromatic rings and are a measure ofaromaticity of a solvent. H.sub.α protons are attached to non-aromaticcarbon atoms attached directly to an aromatic ring structure, e.g.,alkyl groups and naphthenic ring structures. H.sub.β protons areattached to carbon atoms which are in a second position away from anaromatic ring, and H.sub.γ protons are attached to carbon atoms whichare in a third position or more away from an aromatic ring structure.##STR1##

The H_(Ar) protons are important because of their strong solvency power.A high content of H.sub.α protons is particularly significant in apresent invention hydrocarbon solvent, because H.sub.α protons arelabile and are potential hydrogen donors in a solvation process. H.sub.βand H.sub.γ protons are paraffinic in nature and do not significantlycontribute to the ability of a hydrocarbon solvent to solvate asphalticand polymeric materials.

It is particularly preferred that the highly aromatic hydrocarbonsolvent component of the present invention asphaltic composition has ahydrogen content distribution in which the H_(Ar) proton content isbetween about 30 and 50 percent, the H.sub.α proton content is at leastabout 30 percent and the H.sub.α /H.sub.β proton ratio is above about1.4. Concomitantly it is desirable that the H.sub.β proton content isbelow 20 percent and the H.sub.γ proton content is below 13 percent. Itis preferred that the highly aromatic hydrocarbon solvent component ofthe asphaltic composition is a highly aromatic petroleum refineryresiduum solvent having the above defined hydrogen content distribution,and it is especially preferred that the highly aromatic petroleumrefinery residuum solvent is selected from FCC main column bottoms andTCC syntower bottoms.

The proton distribution in examples of various highly aromatichydrocarbon by-product streams are illustrated below.

    ______________________________________                                        Example       H.sub.α                                                                         H.sub.β                                                                         H.sub.γ                                                                       H.sub.Ar                                                                           H.sub.α /H.sub.β           ______________________________________                                        FCC/MCB                                                                       #1            36.0    19.3   12.7  32.0 1.87                                  #2            36.4    13.6   5.2   44.8 2.68                                  #3            18.5    50.0   14.3  17.1 0.37                                  #4            18.1    48.8   18.9  14.2 0.37                                  TCC/Syntower Bottoms                                                          #1            29.8    20.9   7.9   41.4 1.42                                  #2            16.3    48.1   20.0  15.6 0.35                                  Clarified Slurry Oil                                                                        19.4    48.5   16.5  15.5 0.40                                  Agha Jari Resid                                                                             12.0    60.0   24.0  5.0  0.20                                  (850 + °F.)                                                            SRC Recycle Oil                                                                             27.1    14.7   6.9   46.3 1.84                                  Coal Tar      5.      --     --    91.  --                                    ______________________________________                                    

From the foregoing it is noted that hydrocarbons having the same generalprocess derivation may or may not have the desired proton distributionpreviously described hereinabove. For example, FCC/MCB #1 and #2 havethe desired proton distribution while FCC/MCB #3 and #4 do not.

Furthermore, it is not necessary that the highly aromatic hydrocarbonsolvent component of the novel asphalt composition of this invention bederived only from petroleum. In the above table, it may be noted thatSRC recycle solvent closely resembles FCC/MCB #1 and #2, particularly inthe H.sub.α /H.sub.β ratio. The following table, from an articleentitled "Recycle Solvent Techniques for the SRC Process", by R. P.Arderson, appearing in Coal Processing Technology, Volume 2, Am. Inst.of Chem. Engr., pages 130-32 (1975), demonstrates that some SRC recyclesolvents can qualify for use as the highly aromatic hydrocarbon solventcomponent of the present invention asphaltic composition. Shown in thetable are the hydrogen distribution changes which occur during multiplepasses of recycle solvent through the coal extraction step of an SRCprocess. The initial solvent employed was Gulf Carbon Black Feedstock FS120. For comparison purposes, the hydrogen distribution of variousanthracene oils is illustrated.

    ______________________________________                                                  H.sub.α                                                                        H.sub.β                                                                         H.sub.γ                                                                         H.sub.Ar                                                                           H.sub.α /H.sub.β              ______________________________________                                        Gulf FS 120 29.7     31.4   9.2   29.7 0.94                                   Pass 1      30.8     30.2   8.2   30.8 1.02                                     2         31.3     28.4   7.1   33.2 1.10                                     3         29.9     26.7   7.4   36.0 1.12                                     4         30.3     24.7   6.9   38.1 1.23                                     5         30.1     23.9   6.2   39.8 1.26                                     6         28.8     22.3   7.0   41.9 1.29                                     7         28.7     21.2   6.3   43.8 1.35                                     8         29.4     20.1   5.8   44.7 1.46                                     9         29.7     19.3   4.9   46.1 1.54                                     10        30.0     18.8   4.7   46.5 1.60                                     11        29.8     18.8   4.9   46.5 1.58                                   Raw Anthracene                                                                            18.9     3.4    0.6   77.1 5.6                                    Oil                                                                           Partially Hydro-                                                                          20.5     8.6    1.6   69.3 2.4                                    genated Anthracene                                                            Oil                                                                           Anthracene Oil                                                                            23.3     15.2   4.7   56.7 1.53                                   Recycle                                                                       ______________________________________                                    

Although not preferred, recycle solvents such as shown from passes 9-11of the foregoing table may be employed as the highly aromatichydrocarbon solvent component of the present invention asphalticcomposition.

Polymeric Component

A polymeric component is included in the asphaltic binder compositionfor the purpose of imparting improved ductility and resistance tofatigue failure properties to the binder composition. The polymericcomponent is incorporated in the binder composition in a quantitybetween about 1-20 weight percent, based on the combined weight ofasphalt and polymeric components, and preferably in a quantity betweenabout 5-20 weight percent.

For optimal effect, it is essential that the polymeric component issubstantially non-oil resistant and asphalt-soluble in its solubilityproperties. The polymeric component on the average will have a molecularweight in the range between about 5,000 and 10,000,000. Anethylene-vinyl acetate copolymer having a melt index between about20-50, for example, has excellent physical and mechanical qualificationsfor use as the polymeric composition of the invention bindercomposition.

By the term "asphalt-soluble" is meant a polymeric component whichdissolves or is solvated in an amount up to about 80 weight percent whenmixed and heated with an equal weight of the highly aromatic hydrocarbonsolvent. Any high molecular weight fraction of the polymeric componentwhich does not dissolve or solvate, can function advantageously as acompatible suspension phase.

Illustrative of the types of resin materials which can be employed asthe polymeric component are poly(halogenated hydrocarbons), polyolefinsand polyvinyl aryls such as polyvinyl chloride, polyethylene andpolystyrene. Particularly desirable polymeric derivatives are naturaland synthetic rubbers such as plantation rubber, thiokols, neoprenes,nitrile rubbers, styrene rubbers, polybutadiene, acrylate rubbers,polyurethanes, and mixtures thereof which are substantially non-oilresistant and asphalt-soluble.

While it is possible to employ new and unused resin materials as thepolymeric component in the present invention asphaltic bindercomposition, it is particularly advantageous to employ "scrap" or"reclaimed" rubber for economic reasons and for purposes ofenvironmental protection. As employed herein, the term "scrap" rubber ismeant to include "reclaimed" rubber.

The scrap rubber can be in the form of (1) ground whole tire rubber(with or without carcass fibers); (2) unprocessed rubber buffings, i.e.,a byproduct of tire retreading; (3) ground inner tubes; (4) reclaimedrubber; (5) partially devulcanized reclaimed rubber; and the like.

The reclaimed rubber can be devulcanized or partially devulcanized andcan be prepared by the digester process, Heater or Pan process,Lancaster-Banbury process, and other conventional reclaiming processesas more fully described in U.S. Pat. No. 3,891,585.

Whole tire rubber can be ground, screened, and treated to remove metal,cord and fabric therefrom prior to usage in the invention asphalticbinder composition. However, whole used tire carcasses can be comminutedand employed directly without any prior treatment.

The comminuated scrap rubber component can be introduced into theasphaltic binder composition in the form of a fine powder having aparticle size in the range between about -4 mesh and 200 mesh. A processfor production of finely powdered scrap rubber is disclosed in U.S. Pat.No. 2,853,742. It is also convenient and practical to employ the scraprubber in the form of shredded or diced material. The particle size ofthe shaped rubber cubes or pellets can range from about 0.05 inch toabout 0.5 inch in dimensions.

Properties Of The Asphaltic Binder Composition

The invention asphaltic binder composition is conveniently prepared byadmixing and heating together the highly aromatic hydrocarbon solventand non-oil resistant polymeric components of the composition. Ifdesired, the heating cycle can be postponed until the time the asphalticbinder composition is to be applied to a pavement surface. It ispreferred that the heating cycle is of sufficient intensity and durationto completely solubilize and homogenize the admixture of components.

Illustrative of the nominal properties of a present invention asphalticbinder composition is a ring and ball softening point (ASTM D-36)between about 100°-150° F., and a viscosity (ASTM D-2170) between about80-300 centistokes at 275° F.

In a further embodiment, the present invention contemplates theprovision of a ductile asphaltic composition adapted for repairing andsurfacing distressed asphalt pavements which comprises a blend of (1)between about 30-80 weight percent of an asphalt component selected frompaving grade and marginal asphalt materials; (2) between about 10-60weight percent of an aromatic solvent component having a boiling rangeabove about 650° F. and having a hydrogen content distribution in whichthe H_(Ar) proton content is between about 30 and 50 percent, theH.sub.α proton content is at least 30 percent and the H.sub.α /H₆₂proton ratio is above about 1.4; and (3) between about 1-20 weightpercent of a polymeric component which is substantially asphalt-soluble;wherein the said asphaltic composition has a ring and ball softeningpoint in the range between about 110°-185° F., a ductility of more than100 centimeters at 77° F., and a penetration value in the range betweenabout 70-300.

The ductility of the above-defined asphaltic composition is measured inaccordance with ASTM method D 113-44. The penetration values at 77° F.is measured by the standard method of test for penetration of bituminousmaterials (ASTM D 5-52), the penetration values being measured as thetenths of a millimeter that a tapered standard needle (0.14 to 0.16 mmtip diameter) will penetrate the asphalt in five seconds with a 100 gramload.

As defined above, the asphaltic composition contains an asphaltcomponent selected from paving grade and marginal asphaltic materials. Atypical paving grade asphalt exhibits a viscosity-penetration indexhigher than about 2.5×10⁵.

By the term "viscosity penetration index" is meant the product ofviscosity of asphalt in stokes at 140° F. time penetration at 77° F./100g/5 sec. Asphalt stocks which exhibit greater increase inviscosity-penetration index in an air-blowing process are superiorstocks, because a higher viscosity-penetration index value indicatesdisproportionally greater increase in viscosity (or softening point)than the decrease in penetration.

The quality of an asphalt stock for air-blowing can be evaluated at (1)a comparison of viscosity-penetration index at the same penetration; orby (2) a comparison of the response of the asphalt stock to air-blowing,i.e., the slope of viscosity-penetration index versus penetration α, inthe equation log (viscosity-penetration) equals α(penetration)+β, orchange of viscosity penetration index for each penetration number at 45penetration, γ.

It is a particular advantage of the present invention that a marginalasphalt can be employed as the asphalt component in the above-definedcomposition instead of a paving grade asphalt. By the term "marginal"asphalt is meant any of the various types of petroleum refinery asphaltsand natural asphalts which after air-blowing have aviscosity-penetration index lower than about 2.5×10⁵. Marginal asphaltsare generally unsuitable as stocks for paving grade binders.Illustrative of typical sources of marginal asphalt stocks are:

A. Petroleum asphalts

1. Straight-reduced asphalts

a. Atmospheric or vacuum distillation

b. Solvent precipitation

2. Thermal asphalts, as residues from refinery cracking operations

B. Native or natural asphalts

1. Mineral content below 5 percent

a. Asphaltites such as gilsonite, grahamite, and glance pitch

b. Burmudez and other natural deposits

2. Mineral content over 5 percent

a. Rock asphalts

b. Trinidad and other natural deposits

There are two kinds of asphalt stocks which are well-known to have poorqualities for air-blowing treatment:

(1) Residuum of high hydrogen content, i.e., a low carbon-hydrogenratio. This type of stock contains higher paraffinic compounds which aredifficult to convert to resins and asphaltenes via air-blowing.

(2) Short residuum. When more and more valuable distillates are drivenoff from petroleum crudes, the penetration of residua becomes lower, andeventually straight-run asphalt results. If additional distillates areremoved, the resulting short residuum cannot be blown to high viscositywithout exceeding the lower limit of penetration.

Further, because of the exceptional solvating power of the highlyaromatic hydrocarbon solvent component in the above-defined asphalticcomposition, the asphalt component can be introduced in the form ofreclaimed aged pavement asphalt. Aggregate can be included if theasphaltic composition is to be employed to repair pavements whichcontains large fractures and voids, or if a pavement is to beresurfaced.

The following examples are further illustrative of the presentinvention. The reactants and other specific ingredients are presented asbeing typical, and various modifications can be derived in view of theforegoing disclosure within the scope of the invention.

EXAMPLE I

An FCC main column bottoms is topped to yield a residual fraction havinga 650° F. cut point. The residual fraction has a hydrogen contentdistribution in which the H_(Ar) content is 35 percent, the H.sub.αcontent is 37 percent and the H.sub.β content is 18 percent.

A batch of the 650° F. FCC/MCB residual fraction is heated to about 400°F., and to the heated mass there is added ethylene-vinyl acetate (33weight percent vinyl acetate) having a melt index of 43 in sufficientquantity to constitute about 20 weight percent of the total asphalticadmixture. While maintained at a temperature of about 375° F., theasphaltic admixture is spread over a fatigued asphalt pavement whichexhibits a pattern of cracks and fractures. While the spread asphalticadmixture is still plastic, a layer of fine aggregate is applied overthe coated pavement surface. No fatigue cracking is evident when therepaired surface is resubjected to its normal traffic stress.

EXAMPLE II

A marginal asphalt residuum of high paraffinic content(viscosity-penetration index lower than 2.5×10⁵) is heated to 400° F. Tothe heated batch is added ground tire rubber (SBR, -25 to +50 mesh) anda TCC syntower bottoms equivalent in hydrogen content distribution tothe FCC main column bottoms described in Example I, and the heating iscontinued for one hour. The proportions of components are in a weightratio of 40/50/10 of asphalt to TCC syntower bottoms to scrap rubber.

The asphaltic admixture exhibits asphaltic properties at ambienttemperatures. The composition is substantially homogeneous and has aring and ball softening point of 130° F., a ductility of about 110 at77° F. and a penetration value of about 150.

What is claimed is:
 1. In a process for repairing and surfacing brokenasphalt pavement which comprises heating and applying a fluid ductileasphaltic composition to a distressed pavement surface in a sufficientquantity to penetrate and fill void spaces, the improvement being saidductile asphaltic composition comprising a homogeneous blend of (1)between about 30-80 weight percent of an asphalt component selected frommarginal asphalt materials having a viscosity penetration index lowerthan about 2.5×10⁵ ; (2) between about 10-60 weight percent of a highlyaromatic petroleum refinery residuum solvent component having a boilingrange above about 650° F. and having a hydrogen content distribution inwhich the H_(Ar) proton content is between about 30 and 50 percent, theH.sub.α proton content is at least 30 percent and the H.sub.α /H.sub.βproton ratio is above about 1.4; and (3) between about 1-20 weightpercent of a polymeric component which is substantially asphalt-soluble;wherein the said asphaltic composition has a ring and ball softeningpoint in the range between about 110°-185° F., a ductility of more than100 centimeters at 77° F., and a penetration value in the range betweenabout 70-300.
 2. A process in accordance with claim 1 wherein the highlyaromatic solvent component of the binder composition is selected fromFCC main column bottoms and TCC syntower bottoms.
 3. A process inaccordance with claim 1 wherein the polymeric component of the bindercomposition is comminuted scrap rubber.
 4. A process in accordance withclaim 1 wherein the polymeric component of the binder composition is acopolymer of ethylene and vinyl acetate having a melt index betweenabout 20-50.